This invention relates generally to a new low cost design for a multiphase thermally responsive circuit breaker and more particularly to a three-phase motor protector.
In a multiphase motor protector, it has been standard practice to use some array of movable contacts matching up with an equal number of stationary contacts. Then, upon some means of actuation force, pairs of contacts will move into or out of engagement with one another.
Among the several objects of this invention is to provide a protective device that is small and compact, yet long lasting and reliable to provide easier production techniques for such a device and to provide less expensive manufacturing costs and material savings in producing such a device. Other objects and features will be in part apparent and in part pointed out hereinafter.
The device of this invention employs a sole movable contact in a multiphase protector, such as a three-phase motor protector, instead of the normal use of a separate movable contact for each phase. The one movable contact is centrally mounted on a snap-acting bimetallic disc and positioned relative to the three stationary contact terminals which are centered in a cluster so that the one movable contact can make contact with all three terminal contacts at once. Then upon thermal energy being applied or dissipated to or from the bimetallic disc, the movable contact will move into or out of engagement with all three terminal contacts.
The device made in accordance with the invention has the advantage of having fewer parts than conventional protectors and therefore is easy and inexpensive to manufacture. Also the use of only one contact saves material which is very important for both economic and conservation reasons.
The invention accordingly comprises the constructions hereinafter described, the scope of the invention being indicated in the following claims.